Heat exchangers of the plate type are comprised of pairs of preformed plates joined to other pairs at their ends by integral bosses and separated at their middle section by air centers or corrugated fins, the plates and fins all being brazed together so that each pair of plates becomes a tube for carrying refrigerant, the bosses serving as a manifold for permitting refrigerant flow from one tube to another, and the fins facilitating heat exchange between the tubes and air flowing outside the tubes. U.S. Pat. No. 4,470,455 issued to Sacca describes such a plate type heat exchanger in detail.
The assembly of the plate type heat exchanger elements into a core ready for brazing has typically been carried out largely by hand operations. Specifically, the first step is to assemble a fin element between two plates and crimp the plates together into subassemblies where their bosses connect, and then manually stack such subassemblies along with side plates into a fixture which holds each subassembly in place.
It is desirable to enhance the assembly practice by an improved method and machine for assembly. In particular it has been found that the process is improved in terms of automation and in terms of reducing spacing in the fixture if it is begun by joining the plates together into pairs that eventually become tubes and inserting the plate pairs and side plates into a fixture and then inserting the centers between the plates. It is desirable to have a machine to perform the assembly operations to reduce the manufacturing expense and otherwise improve the efficiency of the assembly practice. It has been demonstrated that the machine assembly of plate pairs, air centers and side plates into a pallet is practical.
It is known to automatically assemble other styles of heat exchanger cores as shown in the U.S. Pat. No. 4,321,739 to Martin et al. In Martin et al the tubes are first inserted into blocks carried by chains and the centers are then loaded between the tubes which are well spaced by the blocks. The tubes and centers are gathered together as the blocks are removed from one tube at a time. Thus tubes and centers are arranged in alternate rows and headers are joined to the ends of the tubes and tanks are joined to the headers to couple the tubes together. The tubes do not directly coact and they have smooth exteriors which facilitate the insertion of centers, as contrasted with the plate and center type which requires that the plates each mate with their neighbors as well as to sandwich the air centers. Further, the plate edges protrude in a way to interfere with center insertion so that large spacings between the plates would be required to permit center insertion. The large spacings necessitate a large gathering distance and also allow centers to get out of position so that centers can interfere with the coupling of the plates during the gathering process.